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WELL INSTALLATION AND INTERIM REMEDIAL ACTION REPORT www.arcadis.com FINAL_Forward CHCF (CDCR) Well Installation Report_10182024 18 6 Groundwater Extraction and Treatment System Design Groundwater extraction with ex-situ treatment and disposal is the proposed remedial approach for the portions of the TVOC plume with concentrations of 25 µg/L or greater beneath the CDCR property. The proposed CDCR GWET system design and implementation plan is described below. The implementation of this GWET system as the IRA satisfies the requirements outlined in CAO R5-2017-0703 (RWQCB 2017), Item 3c, which addresses the VOC plume mass beneath the CDCR property. The proposed GWET system includes pumping groundwater from the CDCR intermediate WBZ at four extraction wells (CDCR-EW-2 through CDCR-EW-5). Groundwater will be conveyed to a system compound located at the CDCR property, and treated water will be piped to the existing infiltration basin located at Forward Landfill. The proposed system layout is presented in Figure 8 and d etails of this system and its implementation are provided in the following sections. 6.1 Technology Description Groundwater extraction with ex-situ treatment is a commonly used remedial technology for the treatment of the TVOC plume in groundwater beneath the CDCR property. The extraction of groundwater expedites the rate of groundwater flushing throughout the target treatment zone and additionally creates hydraulic containment to prevent further downgradient migration of impacted groundwater. Groundwater extraction maximizes contaminant transfer between lower and higher permeability lithology and reduces overall remedial timeframes. Although the groundwater flow velocity through lower permeability zones is significantly slower than through high permeability zones, the primary mass flux mechanism through the secondary porosity is often still advection. Groundwater extraction enhances the subsurface seepage velocity and pore volume exchange to increase contaminant mass flux between the lower and higher permeability zones, thereby reducing the overall remedial timeframe. Groundwater extraction is typically paired with an ex-situ groundwater treatment process to remove contaminant mass from extracted groundwater before disposal. Granular activated carbon (GAC) adsorption is a treatment technology often employed for the removal of VOCs from groundwater. GAC is a crude form of graphite that is processed to have a highly porous structure and very high surface area available for VOC adsorption and is often employed for the removal of VOCs from groundwater. The treated groundwater will then be conveyed to an existing infiltration basin on the Forward Landfill property. 6.2 Design Strategy The overall strategy of the IRA is to operate the GWET system with the extraction well layout discussed in Sections 5.4 and 5.5 to provide hydraulic capture of the TVOC plume with concentrations of 25 µg/L or greater beneath the CDCR property. 6.3 Basis of Design Results from previous site characterization activities and extraction well pump testing activities were used as a basis for the design for the IRA at the CDCR property. Common design elements include.